Voice message systems (VMSs), e.g., answering machines and voice mail systems, are commonplace in the modern communications oriented world.
Most VMSs allow a user to obtain message status information by calling the voice messaging system and then entering a mailbox (or account) identifier, a password and/or control signals, e.g., DTMF tones. The retrieval of message status information in this matter represents a polling operation wherein the VMS is periodically contacted and checked for waiting message information.
While polling a VMS for message waiting information is acceptable in many applications, e.g., in the case of home answering machines, a better approach is to provide a user of a VMS a positive indicator of a waiting message without the user having to check for the message. A frequently encountered example of such an indicator is a message waiting light on a telephone which is activated when a message is left for a VMS user and deactivated when the message is accessed or deleted.
Centrex is a telephone service whereby a telephone company associates several independent telephone lines together to provide PBX type functionality, e.g., telephone extension dialing, call forwarding, etc. Centrex features are provided through control of telephone lines and calls using software and a switch located at a telephone central office. For each Centrex subscriber, a separate call processing record is maintained and telephone services are provided according to the information in the call processing record.
Voice mail is sometimes provided as a Centrex service. To provide voice mail to Centrex subscribers, a voice mail system is often located in a telephone office and coupled to the central office switch used to service Centrex subscribers.
A signaling protocol, referred to as the Simplified Message Desk Interface (SMDI), described in Telecordia Technologies document titled “Simplified Message Desk Interface (SMDI)”, Generic Requirements GR-283-CORE, Issue 1, November 1999 was developed to support basic signaling of information between a message storage and retrieval system (MSRS), e.g., a voice message system (VMS), and a stored program controlled switching (SPCS) system such as a central office (C.O.) switch of the type used to provide Centrex service. The SMDI interface uses Frequency Shift Keying (FSK), Phase Shift Keying (PSK) and/or other analog signaling techniques for transmission of information according to an asynchronous serial data transmission protocol. In accordance with the SMDI protocol each word of a SMDI message consists of a start bit (space), a 7-bit standard ASCII character, an even parity bit and a stop bit (mark).
FIG. 1 illustrates a known prior art communications system 10. The communications system 10 includes a public switched telephone network 40, a business premise 23, and a plurality of residential premises 32, 32′, and the Internet 18. The business premise 23 includes multiple offices 24, 24′. Each office includes a computer 26, 26′. Computers 26, 26′ are coupled together and to the Internet 18 by a local area network (LAN) 25. The offices 24, 24′ also include telephones 28, 28′ coupled to a first C.O. switch 48 of the PSTN 40. Telephones 34, 34′, in residential premises 32, 32′, are coupled to a second C.O. switch 60 of the PSTN 40.
The first and second C.O. switches 48, 60 are located in first and second central offices 42, 44 which are coupled together by a high bandwidth communications channel 56, e.g. a fiber optic link. The PSTN 40 includes a service control point (SCP) 46 which stores customer information, e.g., Centrex call processing records (CPRs), used to provide telephone services to subscribers. The SCP 46 is coupled to the first and second C.O. switches 48, 60 via data lines 43, 45.
In order to provide voice messaging services to Centrex service subscribers coupled to the first C.O. switch 48, a voice messaging system (VMS) 50 is coupled to the C.O. switch 48 via a voice channel 54 and a SMDI link 52. Calls to VMS service subscribers which go unanswered for a preselected period of time are supplied to the VMS 50 where the caller is provided the opportunity to leave a message for the called party. The SMDI link 52 is used to convey call data, in the form of SMDI history messages, from the C.O. switch 48 to the VMS 50. The SMDI link 52 is also used to convey message waiting indicator (MWI) control messages from the VMS 50 to the C.O. switch 48.
In particular, when an unanswered call is delivered to the VMS 50, the C.O switch 48 transmits a SMDI call history message to the VMS over the SMDI link 52. FIG. 2 illustrates the format for a standard SMDI history message 200.
The call history message 200 begins with the alphabetic characters MD 202. A 7-digit message line identifier (MLI) 204 follows. The MLI 204 identifies the line to which an incoming call is terminated. It can be, e.g., a 7-digit directory number (DN) assigned to the PSTN or a 7-digit number made up of multi-line hunt group (MLHG) identifier and MLHG position identifier. MLI 204 is followed by a 1 character call type identifier 206 which indicates the reason the call was directed to the VMS. A 10-digit forwarding DN 208 is included in the message 200 when the call has been forwarded. Thus, the forwarding DN 208 is omitted in the case of direct calls. A space 209 separates the forwarding DN 208 from a calling DN number 210. The calling DN 208 is followed by a space and a 1 character calling presentation status field 214. The field 214 is followed by another space 216. A calling name/presentation status field 218 is used to provide the name of the calling party which is obtained when available using known techniques. Some of the information fields may be omitted from the call history message 200 depending on the nature of the call being connected to the VMS 50 and the availability of information to populate the fields.
FIG. 3 illustrates the format of a SMDI MWI control message 300. The message 300 includes an activation request identifier field 302, a space 304 and a subscriber directory number field 306. The activation request identifier field 302 includes the characters OP or RMV to indicate whether the message waiting indicator should be activated (“operated”) or de-activated (“removed”). The subscriber DN field includes a 10-digit directory number which is used to indicate the subscriber whose message waiting indicator is to be controlled. SMDI MWI control messages 300 are terminated by a “!” and a Control D character (not shown).
Use of voice messing IPs such as the VMS 50 is not limited to Centrex applications. The VMS 50 can be used to provide voice messaging services to residential telephone service customers such as users of telephones 34, 34′. Unfortunately, most residential voice messaging service subscribers lack telephones with message waiting lights which are capable of being activated by a C.O. switch.
One of the advantages of Centrex is that it can be used with standard telephones thereby allowing businesses to avoid the investment in more costly phones which support features such as message waiting lights. Accordingly, many business subscribers to voice messaging services provided by telephone companies find themselves confronted with having to call the VMS 50 to check for messages even though the VMS 50 supports a SMDI link 52 to the C.O. switch 48.
In view of the above, it becomes apparent that there is a need for improved methods and apparatus notifying voice messaging service subscribers of waiting messages. It is desirable that at least some notification methods be supported which do not require a subscriber to poll a VMS to be notified of waiting messages. It is also desirable that at least some notification methods be supported which can be used with existing voice messaging systems, e.g., systems which support the use of SMDI. It is further desirable that new message notification methods and apparatus not interfere with existing C.O. notification via the control of message waiting lights on telephones which support such functionality.